prtEvalAuc   Returns the area under the receiver operating curve.
 
    auc = prtEvalAuc(prtClassifier, prtDataSet) returns the area under the
    receiver operating curve. prtDataSet must be a labeled, binary
    prtDataSetStandard object. prtClassifier must be a prtClass object.
 
    auc = prtEvalAuc(prtClassifier, prtDataSet, nFolds) returns the area
    under the receiver operating curve with K-fold cross-validation.
    prtDataSet must be a labeled, binary prtDataSetStandard object.
    prtClassifier must be a prtClass object. nFolds is the number of folds
    in the K-fold cross-validation.
 
    auc = prtEvalAuc(prtClassifier, prtDataSet, xValInds) same as above,
    but use crossValidation with specified indices instead of random folds.
 
    Example:
    dataSet = prtDataGenSpiral;
    classifier = prtClassDlrt;
    auc = prtEvalAuc(classifier, dataSet)